checker: allow for `unsafe {*(p+1) = 22}` (#10557)

vlib/v/checker/checker.v

@@ -1599,6 +1599,9 @@ fn (mut c Checker) fail_if_immutable(expr ast.Expr) (string, token.Position) {
 		ast.StructInit {
 			return '', pos
 		}
+		ast.InfixExpr {
+			return '', pos
+		}
 		else {
 			if !expr.is_lit() {
 				c.error('unexpected expression `$expr.type_name()`', expr.position())

vlib/v/tests/pointers_test.v

@@ -7,6 +7,8 @@ fn test_pointer_arithmetic() {
 		assert 2 == *parr
 		parr++
 		assert 3 == *parr
+		parr_add_one := *(parr + 1)
+		assert parr_add_one == 4
 		assert *(parr + 1) == 4
 	}
 }